PCM controlled charging system

ABSTRACT

A method of controlling an alternator in a marine propulsion system includes receiving a battery voltage level of a battery charged by the alternator, receiving a throttle demand value, determining whether the throttle demand value exceeds a demand threshold, and determining whether the battery voltage level exceeds a threshold minimum battery voltage. If the throttle demand value exceeds the demand threshold and the battery voltage level exceeds the threshold minimum battery voltage, then the alternator is controlled to reduce the charge current output to the battery and reduce engine output power utilized by the alternator.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/403,950, filed Jan. 11, 2017, which is incorporated herein byreference in entirety.

BACKGROUND

The following U.S. Patents and Applications provide backgroundinformation and are incorporated herein by reference in entirety.

U.S. Pat. No. 5,481,178 discloses a circuit and method for controlling aswitching voltage regulator having (1) a switch including one or moreswitching transistors and (2) an output adapted to supply current at aregulated voltage to a load including an output capacitor. The circuitand method generates a control signal to turn said one or more switchingtransistors OFF under operating conditions when the voltage at theoutput is capable of being maintained substantially at the regulatedvoltage by the charge on the output capacitor. Such a circuit and methodincreases the efficiency of the regulator circuit particularly at lowaverage current levels.

U.S. Pat. No. 6,273,771 discloses a control system for a marine vesselthat incorporates a marine propulsion system that can be attached to amarine vessel and connected in signal communication with a serialcommunication bus and a controller. A plurality of input devices andoutput devices are also connected in signal communication with thecommunication bus and a bus access manager, such as a CAN Kingdomnetwork, is connected in signal communication with the controller toregulate the incorporation of additional devices to the plurality ofdevices in signal communication with the bus whereby the controller isconnected in signal communication with each of the plurality of deviceson the communication bus. The input and output devices can each transmitmessages to the serial communication bus for receipt by other devices.

U.S. Pat. No. 6,652,330 discloses a method for controlling theelectrical system of a marine vessel that comprises the steps ofmeasuring a battery potential, comparing the battery potential to athreshold voltage magnitude, and then disconnecting one or more of aplurality of electrical power consuming devices when the voltagepotential is less than the threshold voltage magnitude. This is done toavoid the deleterious condition wherein an engine of the marine vesselis operating at idle speed and attempting to charge the battery while aplurality of electrical power consuming devices are operating anddrawing sufficient current from the alternator to prevent the propercharging of the battery. In these circumstances, the battery potentialcan actually be depleted as the battery attempts to provide theadditional required electrical current for the loads.

U.S. Pat. No. 7,812,467 discloses a smart alternator control circuit andmethod limiting alternator load on an internal combustion engine.

U.S. Pat. No. 7,941,253 discloses a marine propulsion drive-by-wirecontrol system controls multiple marine engines, each one or more PCMs,propulsion control modules for controlling engine functions which mayinclude steering or vessel vectoring. A helm has multiple ECUs,electronic control units, for controlling the multiple marine engines. ACAN, controller area network, bus connects the ECUs and PCMs withmultiple PCM and ECU buses. The ECU buses are connected throughrespective isolation circuits isolating the respective ECU bus fromspurious signals in another ECU bus.

SUMMARY

This Summary is provided to introduce a selection of concepts that arefurther described below in the Detailed Description. This Summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

In one embodiment, a marine propulsion system includes an engineeffectuating rotation of an output shaft at an engine output power, abattery, and an alternator having a rotor driven into rotation by theoutput shaft such that the alternator utilizes a portion of the engineoutput power to generate a charge current to the battery. The marinepropulsion system includes a control system that receives a throttledemand value and determines whether the throttle demand value exceeds ademand threshold. The control system controls the alternator to reducethe charge current output to the battery and reduce the portion of theengine output power utilized by the alternator when the throttle demandvalue exceeds the demand threshold.

In one embodiment, a method of controlling an alternator in a marinepropulsion system includes receiving a battery voltage level of abattery charged by the alternator, receiving a throttle demand value,determining whether the throttle demand value exceeds a demandthreshold, and determining whether the battery voltage level exceeds athreshold minimum battery voltage. If the throttle demand value exceedsthe demand threshold and the battery voltage level exceeds the thresholdminimum battery voltage, then the alternator is controlled to reduce thecharge current output to the battery and reduce engine output powerutilized by the alternator.

Another embodiment of a marine propulsion system includes an engineeffectuating rotation of an output shaft, a battery, an alternatorhaving a rotor driven into rotation by the output shaft, and atemperature sensor that measures a temperature associated with theengine. The marine propulsion system further includes a control systemthat receives the temperature from the temperature sensor and determineswhether the temperature exceeds a temperature threshold. If thetemperature threshold is exceeded, then the control system controls thealternator to reduce the charge current output to the battery.

One embodiment of a method of controlling an alternator in a marinepropulsion system includes receiving a temperature from a temperaturesensor, wherein the temperature is at least one of an intake airtemperature, an oil temperature, and a coolant temperature. The methodincludes determining whether the temperature exceeds a temperaturethreshold, and controlling the alternator to reduce the charge currentoutput to the battery when the temperature exceeds the temperaturethreshold.

Various other features, objects, and advantages of the invention will bemade apparent from the following description taken together with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is described with reference to the followingFigures.

FIG. 1 is a schematic diagram of a marine propulsion system according toone embodiment of the present disclosure.

FIG. 2 is a graph depicting horse power consumption and charging currentoutput for an exemplary alternator.

FIGS. 3-7 depict various embodiments of methods of controlling analternator in a marine propulsion system.

DETAILED DESCRIPTION

As electrical demand in marine vessels increase, larger and largercapacity alternators are being utilized. For example, marine vesselshave an ever increasing number of electronic devices for navigation andon-board computing, as well as an ever increasing number of accessorydevices that require high current draw, such as stereo systems, largeuser interface displays, large bilge pumps, as well as electricaloutlets to be utilized by passengers on the vessel. These highercapacity alternators provide sufficient charging output to the batteryso that the various accessory devices can be operated effectively.However, through extensive experience and research in the relevantfield, the inventor has recognized that such large capacity alternatorshave an unintended consequence of reducing the available horse poweroutput from the engine for driving the propeller to propel the marinevessel. Another problem recognized by the inventor is that the highercapacity alternators produce significant heat that can contribute tooverheating of the engine.

In view of his recognition of foregoing problems and challenges, theinventor developed the disclosed marine propulsion system utilizing amethod of controlling an alternator based on a demand threshold on theengine and/or based on an engine-related temperature measurement, suchas a temperature measurement from a temperature sensor under the cowl.The inventor recognized that the alternator can be controlled to reducethe charging output to the battery, such as turning off the chargingoutput altogether, during peak demand in order to increase the amount ofpower available to propel the marine vessel.

FIG. 2 provides a graph showing a charging output to a battery and acorresponding power consumption for an exemplary alternator. Line 35depicts an exemplary charging current output from an alternator to abattery based on engine RPM, and specifically charging output in amperesfrom the exemplary alternator at a range of engine RPM from 500 RPM(exemplary idle setpoint) to about 6,000 RPM (exemplary maximum engineRPM). The dashed line 36 represents a corresponding horsepowerconsumption of the exemplary alternator at the same range of RPMs. Inthe depicted example, the alternator consumes approximately 0.5horsepower at idle and consumes about 6.25 horsepower at maximum engineRPM.

The inventor has recognized that some or all of the horsepower consumedby the alternator could be better utilized during peak power demand toallow more power to be delivered to the propeller, such as during heavyacceleration demand or when operating at wide open throttle. This may beespecially valuable at higher engine RPMs, where an increasing amount ofhorse power is consumed with little gain in charging output to thebattery. Accordingly, the inventor developed an alternator controlalgorithm that utilizes throttle demand values, such as throttle leverposition or engine RPM setpoint, as control inputs to reduce thehorsepower consumed by the alternator during peak demand times. Forexample, if maximum power output is being requested by the operator,such as during hard acceleration or maximum throttle demand, the voltagesetpoint for controlling the alternator can be reduced resulting in lessload on the engine from the alternator and more power available topropel the marine vessel. Such control may be provided based on thethrottle demand from the operator, as well as based on a battery voltagelevel of the battery. For example, if the battery voltage level dropsbelow a threshold minimum battery voltage during a high power demandevent, the voltage setpoint for controlling the alternator may begradually increased to maintain the battery voltage at or above thethreshold minimum battery voltage. When the power demanded by theoperator decreases, such as below a demand threshold, the voltagesetpoint may be gradually increased back to its normal state.Alternatively or additionally, the voltage setpoint for controlling thealternator may be reduced for a period of time upon detection of a highthrottle demand from the operator, and thus the alternator may return tonormal operation after expiration of the predetermined period of time.

Additionally, the inventor also recognized that the alternator can becontrolled to increase performance and engine protection functions byallowing the alternator output to be reduced when the under-cowltemperature conditions are high such that additional heat outputted bythe alternator can have deleterious effects. Accordingly, the inventoralso developed an alternator control algorithm utilizes temperaturemeasurement, such as engine temperature or air temperature to controlthe alternator to reduce the alternator output when the temperatures areabove an acceptable threshold temperature, thereby to create less heatfrom the alternator during high under-cowl ambient conditions.

FIG. 1 depicts an exemplary embodiment of a marine propulsion system 4configured to provide the alternator control functionality describedherein. In the depicted embodiment, a propulsion device 6 propels themarine vessel 2. While the propulsion device 6 is depicted as anoutboard motor, in other embodiments the propulsion device 6 may be anydevice that propels the marine vessel, such as an inboard drive,inboard/outboard drive, stern drive, jet drive, or the like. Thepropulsion device 6 includes an engine 8, such as an internal combustionengine, and an engine control module (ECM) 9 that monitors and controlsthe engine 8. The engine 8 drives rotation of the propulsor 10, such asa propeller or impeller, in order to propel the marine vessel 2 throughthe water. The propulsion device 6 further includes one or moretemperature sensors 18, which in the depicted embodiment include an oiltemperature sensor 18 a, coolant temperature sensor 18 b, and intake airtemperature sensor 18 c sensing the temperature of the air entering theintake manifold of the engine 8.

In addition to driving the propulsor 10 to propel the marine vessel 2,the engine 8 output also drives the alternator 12 which converts therotational motion outputted by the engine 8 into electrical energy tocharge the battery 14, which in turn powers the engine (such as atstartup) as well as other accessory devices described above. Forexample, the crank shaft of the engine 8 may drive the rotor of thealternator 12, e.g., by a pulley belt, to generate electrical energy forcharging the battery and/or for use by the engine 8. As is typical, thealternator has a stator supplying output power through output diodes.Some of the output power is supplied back to the alternator in order togenerate a field current, enabling generation of electrical energy uponrotation of the rotor. Accordingly, the alternator causes a load on theengine that absorbs horsepower from the engine output, as depicted inFIG. 2. In general, the greater the engine RPM, the faster that therotor is turned and thus the greater the amount of horsepower utilizedby the alternator 12. Therefor, the alternator 12 outputs more outputcurrent to charge the battery 14 at higher engine RPMs. However, theload on the engine also correlates to the field current, and thusreducing the field current also reduces the amount of engine outputpower consumed by the alternator.

The alternator 12 is controlled by an alternator controller 13, whichmay provide digital and/or analog control of the alternator. In oneembodiment, the alternator controller 13 may be a smart alternatorcontrol circuit responsive to the ECM 9 and/or the helm control module(HCM). The alternator controller 13 controls the amount of load that thealternator 12 puts on the engine 8 by limiting the charge current outputto the battery 14 from the alternator 12. Specifically, the alternatorcontroller 13 limits the load imposed by the magnetic field on the rotorby reducing the field current supplied as feedback to the alternator 12.Thereby, the amount of horsepower absorbed by the alternator 12 isreduced, as is the charge current outputted by the alternator 12. Thealternator controller 13 is typically configured to control thealternator 12 based on the voltage level of the battery 14, such as thevoltage measured by battery voltage sensor 16. For example, thealternator controller 13 may be configured to maintain the batteryvoltage level within a predetermined amount of a voltage setpoint.

The propulsion system 4 further includes one or more propulsion controldevices, such as a throttle lever 22 utilized to control the speed ofthe marine vessel 2. As is standard, the throttle lever 22 is movable ina forward direction to increase the speed of the marine vessel. A leverposition sensor 24 senses a position of the throttle lever 22 andcommunicates the position to a control module, which in the depictedembodiment is a helm control module (HCM) 20. The throttle lever 22 ismovable between a neutral position (such as commanding that a gearsystem of the propulsion device 6 is in neutral) and a full throttleforward position. This range of motion of the throttle lever 22 may beexpressed as a percentage, for example, between 0% associated with theneutral position and 100% associated with the full forward throttleposition of the throttle lever 22.

Accordingly, an operator provides a throttle demand input to the systemby moving the throttle lever 22. A high throttle demand may bedetermined by comparing the position of the throttle lever 22 to athreshold throttle position requiring high horsepower output, such ashigher than the available horsepower output when the alternator 12 isconsuming a significant amount of horsepower. For example, the demandthreshold may be a threshold lever position, such as a throttle leverposition above 90% or above 95%. In other embodiments, the demandthreshold may be set higher or lower depending on the overallconfiguration of the system 4.

Alternatively or additionally, the demand threshold may be defined as athreshold increase in throttle lever position. For example, if theoperator moves the throttle lever 22 forward rapidly, demanding quickacceleration of the marine vessel 2, the portion of the engine outputpower utilized by the alternator may be reduced in order to divert morehorsepower to accelerating the marine vessel 2. Accordingly, the demandthreshold may be a threshold increase in the position of the throttlelever 22 in a given amount of time, above which the output of thealternator 12 is reduced. For example, the helm control module 20 maydetermine the derivative, or change, between two or more consecutivethrottle lever positions measured by the lever position sensor 24 todetermine a rate of change of the throttle lever 22. That rate of changemay be compared to a threshold rate of change in order to determinewhether the throttle demand value exceeds the demand threshold. Toprovide just one example, the demand threshold may be 50% of the totalforward throttle range (between 0% and 100% forward throttle leverposition) per second. If the throttle demand exceeds the threshold, thenthe alternator 12 is controlled as described herein.

In other embodiments, the throttle demand value may be some other valueassociated with the throttle demanded by the operator, or by anautopilot control module controlling propulsion of the marine vessel 2.For example, the throttle demand value may be an engine RPM setpointassociated with the throttle lever 22 position and/or determined by anautopilot system. Likewise, the demand threshold may be an engine RPMsetpoint value against which the demand threshold engine RPM setpointcan be compared. Similarly, the demand threshold may be a thresholdincrease in engine RPM setpoint. In such an embodiment, a change inengine RPM setpoint over a predetermined time period may be calculated.If a sudden acceleration is demanded then the change in engine RPMsetpoint will suddenly increase. If the increase in engine RPM setpointexceeds the threshold, then the alternator reduction strategy describedherein will be employed.

In still other embodiments, the throttle demand value and correspondingdemand threshold may be any other value representing the demand on theengine 8, such as engine load, the amount of output power demanded,percent of available power demanded, or the like.

The alternator control strategy is implemented by a control system onthe marine vessel 2 which may include one or more control modules orother control circuitry. In the depicted embodiment, the control system30 includes the HCM 20, ECM 9, and alternator controller 13. The HCM 20,alternator controller 13, and ECM 9 are communicatively connected suchthat control signals can be communicated therebetween. For example, thecontrol modules 20, 13, 9 of the control system 30 may be operating as aCAN network, such as exemplified in U.S. Pat. No. 6,273,771. In otherembodiments, the modules in the control system 30 may operate as a LocalInterconnect Network (LIN) bus. In still other embodiments,communication between the ECM 9 and HCM 20 may be via CAN bus protocols,and communication to the alternator controller 13 from the other controlmodules 9, 20 may be via a LIN bus communication protocol (for example).In still other embodiments, the control modules within the controlsystem 30 may communicate via wireless communication, which may be byany of various available wireless communication protocols.

The systems and methods described herein may be implemented with one ormore computer programs executed by one or more processors, which may alloperate as part of a single control system 30, or even a single controlmodule comprising the control system 30. The computer programs includeprocessor-executable instructions that are stored on a non-transitorytangible computer readable medium. The computer programs may alsoinclude stored data. Non-limiting examples of the non-transitorytangible computer readable medium are nonvolatile memory, magneticstorage, and optical storage.

As used herein, the term control module may refer to, be part of, orinclude an application-specific integrated circuit (ASIC), an electroniccircuit, a combinational logic circuit, a field programmable gate array(FPGA), a processor (shared, dedicated, or group) that executes code, orother suitable components that provide the described functionality, or acombination of some or all of the above, such as in a system-on-chip.The term module may include memory (shared, dedicated, or group) thatstores code executed by the processor. The term code, as used herein,may include software, firmware, and/or microcode, and may refer toprograms, routines, functions, classes, and/or objects. The term shared,as used above, means that some or all code from multiple modules may beexecuted using a single (shared) processor. In addition, some or allcode to be executed by multiple different processors may be stored by asingle (shared) memory. The term group, as used above, means that someor all code comprising part of a single module may be executed using agroup of processors. Likewise, some or all code comprising a singlemodule may be stored using a group of memories.

FIGS. 3-7 represent various embodiments of a method 60 of controlling analternator 12 to reduce engine output power utilized by the alternatorwhen the throttle demand value exceeds the demand threshold. FIGS. 3-5provide exemplary embodiments of methods 60 of controlling thealternator 12 based on throttle demand value. In FIG. 3, a throttledemand value is received at step 62. Steps are executed at step 64 todetermine whether the throttle demand value exceeds the demandthreshold. If not, then no action is taken and the throttle demand valuecontinues to be monitored. Once the throttle demand value exceeds thedemand threshold, the charge current outputted from the alternator 12 isreduced at step 66 to reduce the engine output utilized by thealternator 12. Exemplary embodiments of the method depicted at FIG. 3are provided at FIGS. 4 and 5.

FIG. 6 provides another exemplary method 60 of controlling an alternatorin a marine propulsion system 4. A temperature associated with theengine is received at step 100 and is compared to a thresholdtemperature at step 102. If the threshold temperature is exceeded, thenthe charge current outputted by the alternator 12 is reduced at step 104to reduce heat output by the alternator. For example, the field currentsupplied to the alternator 12 may be reduced to zero, thereby reducingthe charge current outputted by the alternator 12 to zero andsignificantly reducing the heat generated by the alternator 12. FIG. 7depicts another embodiment of the method generally depicted anddescribed at FIG. 6.

The methods depicted at FIGS. 3-7 are carried out by the marinepropulsion system 4 according to instruction generated by the controlsystem 30. As described above, the control system 30 may include one ormore control modules comprising executable instructions that carry outthe steps described herein. In various embodiments of the control system30, the instructions may be variously divided among one or more controlmodules, which in the depicted exemplary embodiment include the ECM 9,HCM 20, and alternator controller 13.

FIG. 4 depicts an embodiment of a method 60 of controlling an alternator12 in the marine propulsion system 4 based on throttle demand. Athrottle lever position is received at step 70. For example, a positionmeasurement may be received by the HCM 20 from the lever position sensor24 associated with the throttle lever 22. The throttle lever position iscompared to a threshold throttle lever position at step 72, which in thedepicted embodiment is 90%. If the threshold throttle lever position isgreater than 90%, then step 73 is executed to reduce the charge setpointby setting the charge setpoint equal to a threshold minimum batteryvoltage. Namely, the setpoint for controlling the battery voltage is setat a threshold minimum causing the alternator to reduce its chargecurrent output, perhaps to zero, until such time as the battery voltagelevel reaches the threshold minimum battery voltage. The method thencontinues to step 78.

If the throttle lever position does not exceed the 90% demand thresholdat step 72, then a change in lever position is determined at step 74.For example, the current throttle lever position received at step 70 maybe compared to one or more previously-received throttle lever positionsto determine an amount that the throttle lever position has changedand/or a rate of change. Instructions are executed at step 76 todetermine whether the throttle lever position has increased by more thanthe threshold increase. Similarly, instructions may be executed todetermine whether the rate of change of the throttle lever exceeds athreshold rate of change in the positive, accelerating, direction. Ifthe threshold increase is not exceeded at step 76 then the controlsystem 30 executes step 79, where the charge setpoint is set equal tothe normal charge set point for the battery, and thus the alternator 12resumes or continues its normal charging operation. The system thenreturns to step 70 to continue to monitor the throttle lever position.

If the threshold throttle lever is exceeded, then steps are executed atstep 77 to make the charge setpoint equal to the threshold minimumbattery voltage. In the exemplary embodiment, the charge set point ismade equal to the threshold minimum battery voltage for a predeterminedperiod of time. For example, the predetermined period of time may be apreset time period that correlates with the amount of time estimated forthe engine RPM to reach the demanded engine RPM—namely, for the marinevessel to reach the demanded speed corresponding to the throttle leverposition. For example, the predetermined time period may be determinedby accessing a lookup table of time periods based on the throttle leverposition increase. In another embodiment, the predetermined time periodmay be a single set time period for which the alternator is turned offin order to divert additional horsepower to the propeller during theinitial period of acceleration. The alternator is then controlled basedon the charged setpoint. Accordingly, the charge current output from thealternator 12 to the battery 14 is reduced until such time as thepredetermined time period has expired, the battery voltage level reachesthe threshold minimum battery voltage, or the throttle demand no longerexceeds the relevant thresholds.

FIG. 5 depicts another embodiment of a method 60 of controlling analternator 12 in a marine propulsion system 4. An RPM setpoint isreceived at step 80, such as an RPM setpoint associated with the currentposition of the throttle lever 22 as measured by the lever positionsensor 24. For example, the position may be received by the HCM 20 fromthe lever position sensor 24, and the HCM may determine the engine RPMsetpoint associated with the received throttle lever position. A batteryvoltage level is also received at step 81, such as from the batteryvoltage sensor 16. Instructions are executed at step 82 to determinewhether the engine RPM setpoint received at step 80 is greater than orequal to the demand threshold, which is a threshold RPM setpoint. Toprovide just one example, the threshold engine RPM setpoint could be avalue equal to 90% of the maximum RPM of the engine 8. If the thresholdengine RPM setpoint is exceeded then the system continues to step 88.

If not, then instructions are executed at step 84 to determine an engineRPM setpoint increase, such as by comparing the received engine RPMsetpoint to previously-received engine RPM setpoints. The engine RPMsetpoint increase is then compared to a threshold engine RPM increase atstep 86. If the demand threshold is exceeded then the system continuesto execute step 88. If the demand threshold is not exceeded then thecharge setpoint is set to a value that is greater than the batteryvoltage level, such as to the normal setpoint for maintaining thebattery 14. The control system 30 then continues to monitor the engineRPM setpoint to see if the aforementioned thresholds are exceeded.

At step 88, instructions are executed to determine whether the batteryvoltage level received at step 81 from the battery voltage sensor 16exceeds a threshold minimum battery voltage. The threshold minimumbattery voltage threshold is a setpoint below which the charge currentoutput of the alternator 12 to the battery 14 will not be reduced inorder to divert horsepower to turning the propulsor 10. To provide justone example, the threshold minimum battery voltage may be set to 12volts. Preferably, the threshold minimum battery voltage is a valueabove the amount of battery power needed to start the engine 8, such asif the engine were to stall or be turned off during the execution ofthis method. If the battery voltage is not greater than the thresholdminimum battery voltage, then step 94 is executed to set the chargesetpoint above the battery voltage level, thus to provide a chargecurrent output from the alternator 12 to charge the battery 14.

Assuming that the battery voltage level is greater than the thresholdminimum battery voltage, then a reduced charge setpoint is determined atstep 90. In various embodiments, the reduced charge setpoint may be apredetermined value, such as the threshold minimum battery voltage orzero volts, or it may be a value determined based on the battery voltagelevel and/or the throttle demand value. For example, the reduced chargesetpoint may be established based on the magnitude of the throttledemand value and/or the difference between the throttle demand value andthe demand threshold. For example, if the throttle demand value wellexceeds the demand threshold then the charge setpoint might be set low,such as to the threshold minimum battery voltage or to zero volts.Conversely, if the throttle demand value barely exceeds the threshold,the reduced charge setpoint might be set at or below the current batteryvoltage level received at step 81. In that situation, the chargingoutput of the alternator 12 would be reduced or eliminated briefly, butwould soon resume once the battery charge level decreased a bit. Instill other embodiments, the reduced charge set point may be set to apredetermined amount below the current battery voltage level. Thealternator 12 is then controlled based on the charge setpoint based onstep 92. For example, the charge setpoint may be determined at eitherthe ECM 9 or the HCM 20, and then communicated to the alternatorcontroller 13, which controls the alternator based on the receivedcharged setpoint.

FIGS. 6 and 7 depict an embodiment of the method 60 for controlling thealternator 12 based on temperature under the cowl. FIG. 6 is discussedabove. In the embodiment depicted in FIG. 7, three different temperaturevalues are received and compared to respective threshold temperatures.Oil temperatures are received at step 106, such as from oil temperaturesensor 18 a. The oil temperature is then compared to a threshold oiltemperature at step 107. Coolant temperature is received at step 108,such as from coolant temperature sensor 18 b, and then compared to athreshold coolant temperature at step 109. Intake air temperature isthen received at step 110, such as from intake temperature sensor 18 c,and then compared to a threshold intake air temperature at step 111. Ifany of the threshold oil temperature, threshold coolant temperature, orthreshold intake air temperature is exceeded, then a reduced chargesetpoint is determined at step 112. As described above, the reducedcharge setpoint may be a predetermined setpoint value, or it may bedetermined based on the offending temperature measurement and/or thecurrent battery voltage level. In one embodiment, the reduced chargesetpoint may be set equal to zero volts, such as to turn off the fieldcurrent delivered to the alternator 12 and minimize the heat generatedby the alternator activity. Thereby, the alternator will not contributeto the high under-cowl temperature. The alternator is then controlledbased on the charge setpoint at step 113.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to make and use the invention. Certain terms have been used forbrevity, clarity and understanding. No unnecessary limitations are to beinferred therefrom beyond the requirement of the prior art because suchterms are used for descriptive purposes only and are intended to bebroadly construed. The patentable scope of the invention is defined bythe claims, and may include other examples that occur to those skilledin the art. Such other examples are intended to be within the scope ofthe claims if they have features or structural elements that do notdiffer from the literal language of the claims, or if they includeequivalent features or structural elements with insubstantialdifferences from the literal languages of the claims.

I claim:
 1. A marine propulsion system comprising: an engineeffectuating rotation of an output shaft; a battery; an alternatorhaving a rotor driven into rotation by the output shaft and that outputsa charge current to the battery; at least a first temperature sensorthat measures an under-cowl air temperature, an oil temperature, or acoolant temperature; a control system configured to: receive thetemperature; determine whether the temperature exceeds a temperaturethreshold; and control the alternator to reduce the charge currentoutput to the battery when the temperature exceeds the temperaturethreshold.
 2. The marine propulsion system of claim 1, wherein thecontrol system is further configured to: receive a battery voltage levelof the battery; determine a reduced charge setpoint for the battery; andcontrol the alternator based on the reduced charge setpoint.
 3. Themarine propulsion system of claim 2, wherein the control systemdetermines the reduced charge setpoint based on the battery voltagelevel.
 4. The marine propulsion system of claim 2, wherein the controlsystem determines the reduced charge setpoint to be equal to apredetermined setpoint value when the temperature exceeds thetemperature threshold.
 5. The marine propulsion system of claim 4,wherein the control system maintains the reduced charge setpoint at thepredetermined setpoint value until the temperature is less than thetemperature threshold.
 6. The marine propulsion system of claim 1,wherein the first temperature sensor includes least one of an intake airtemperature sensor, an oil temperature sensor, and a coolant temperaturesensor.
 7. The marine propulsion system of claim 6, further comprisingat least a second temperature sensors, wherein the second temperaturesensor includes a different one of the intake air temperature sensor,the oil temperature sensor, and the coolant temperature sensor than thefirst temperature sensor.
 8. The marine propulsion system of claim 7,wherein the control system determines whether the temperaturemeasurement from the first temperature sensor exceeds a firsttemperature threshold, and whether a temperature measurement from thesecond temperature sensor exceeds a second temperature threshold,wherein the first and second temperature thresholds are differentvalues.
 9. A method of controlling an alternator in a marine propulsionsystem, the method comprising: receiving a temperature from atemperature sensor measuring an under-cowl air temperature; determiningwhether the temperature exceeds a temperature threshold; and controllingthe alternator to reduce a charge current output to a battery when thetemperature exceeds the temperature threshold.
 10. The method of claim9, further comprising determining a reduced charge setpoint for thebattery; wherein the step of controlling the alternator to reduce thecharge current output to the battery includes controlling the alternatorbased on the reduced charge setpoint.
 11. The method of claim 10,wherein the reduced charge setpoint is determined based on a currentbattery voltage level of the battery.
 12. The method of claim 11,wherein the reduced charge setpoint is determined to be equal to apredetermined setpoint value when the temperature exceeds thetemperature threshold.
 13. The method of claim 12, wherein thepredetermined setpoint value is 0 volts.
 14. The method of claim 13,further comprising maintaining the reduced charge setpoint at thepredetermined setpoint value until the temperature is less than thetemperature threshold.
 15. The method of claim 9, wherein thetemperature is at least one of an under-cowl air temperature, an oiltemperature, and a coolant temperature.
 16. The method of claim 15,further comprising measuring the under-cowl air temperature with intakeair temperature sensor sensing the temperature of the air entering anintake manifold of an engine.
 17. A method of controlling an alternatorin a marine propulsion system, the method comprising: receiving a firsttemperature from a first temperature sensor measuring one of anunder-cowl air temperature, an oil temperature, or a coolanttemperature; determining whether the temperature exceeds a firsttemperature threshold; and controlling the alternator so as to reduceheat output of the alternator when the first temperature exceeds thefirst temperature threshold.
 18. The method of claim 17, wherein thestep of controlling the alternator includes reducing a charge currentoutput to a battery.
 19. The method of claim 17, further comprising:receiving a battery voltage level of the battery; determining a reducedcharge setpoint for the battery based on the battery voltage level;wherein the step of controlling the alternator to reduce the heat outputto the battery includes controlling the alternator based on the reducedcharge setpoint.
 20. The method of claim 17, further comprising:receiving a second temperature from a second temperature sensormeasuring a different one of the under-cowl air temperature, the oiltemperature, or the coolant temperature than the first temperaturesensor; determining whether the second temperature exceeds a secondtemperature threshold, wherein the first and second temperaturethresholds are different values; and controlling the alternator so as toreduce the heat output of the alternator when either the firsttemperature exceeds the first temperature threshold or the secondtemperature exceeds the second temperature threshold.